Method for setting anchoring bolts in mines

ABSTRACT

A method for installing a roof bolt in a mine, which method comprises: (i) drilling a hole in the roof of a mine; (ii) inserting a resin cartridge having a skin into the hole; (iii) inserting a bolt into the hole and which comprises employing in the hole a tool having one or more sharp elements and wherein the insertion of the bolt causes the tool to puncture the cartridge and prevent the skin from expanding against the wall of the hole.

FIELD OF THE INVENTION

[0001] This invention relates to equipment for use in mines, moreparticularly to roof bolts and a method for using same.

BACKGROUND OF THE INVENTION

[0002] Roof bolts are well known in the mining industry and areextensively employed for consolidating the roof and providing anchoringpoints and support. Their use involves drilling a hole in the roof ofthe mine and inserting into the hole a resin filled cartridge. The resinfilled cartridges are also well known and comprise a curable resin and acatalyst for the resin contained within a sausage-like skin. In the nextstep of the installation a bolt is inserted which pierces the skin andpenetrates the resin. The bolt is usually spun to mix the resin andcatalyst and, once mixed, the resin cures and sets.

PROBLEM TO BE SOLVED BY THE INVENTION

[0003] There is a long standing problem in coal mining, particularlywhen employing small diameter bolts, of a phenomenon called glovefingering. The problem arises when is the bolt is inserted into the holepressurising the cartridge and forcing the skin to the hole wall andthen boring a hole through the contents of the cartridge leaving theskin intact. The result is that there is little direct contact of thewall by the resin and hence a less than optimum anchorage.

[0004] Previous attempts to solve the problem have involved the use of athinner skin to contain the resin, coarse filler in the cartridge andslash cut bolts. However these have not generally been successful.

[0005] There have also been proposals to improve the mixing of thecontents of the cartridge.

[0006] For example it has been proposed to:

[0007] (i) provide metal coils spiralling around and attached to theroof bolt

[0008] (ii) provide enlarged cylindrical sections of the roof bolt, forexample a tubular sleeve around the bolt itself to decrease the annulusbetween the bolt and the bore hole in an effort to improve shear mixingwhen the bolt is spun,

[0009] (iii) retaining washers and/or clips around the leading portionof the anchor bolt which retains the resin in the upper portion of thebore hole to assist anchorage of the expansion shell and

[0010] (iv) a washer or ferrule crimped on the end of a cable bolt toimprove the shear mixing upon insertion.

[0011] These earlier proposals are described in U.S. Pat. Nos.4,194,858; 4,516,886; 4,664,561; 4,655,645; 4,704,053; 5,042,961;5,052,861; 5,076,734; 5,259,703 and 5,378,087.

[0012] However none of these earlier proposals addresses the problem ofglove fingering mentioned above.

[0013] The present invention provides a solution to this problem by theuse of a device to puncture the skin of the cartridge and therebyimprove the contact between the resin and the wall of the bore hole.

SUMMARY OF THE INVENTION

[0014] According to the present invention there is provided a method forinstalling a roof bolt in a mine which method comprises:

[0015] (i) drilling a hole in the roof of a mine

[0016] (ii) inserting a resin cartridge having a skin into the hole

[0017] (iii) inserting a bolt into the hole and which comprisesemploying in the hole a tool having one or more sharp elements andwherein the insertion of the bolt causes the tool to puncture thecartridge and prevent the skin from expanding against the wall of thehole.

[0018] According to another aspect of the present invention there isprovided an assembly comprising:

[0019] a cartridge and attached to one end thereof a tool having a sharpelement which on the application of pressure in the bore hole is capableof puncturing the skin of the cartridge and depressurising thecartridge.

ADVANTAGEOUS EFFECT OF THE INVENTION

[0020] The use of the invention improves the contact of the resin withthe wall of the bore hole and thereby provides an improved anchor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1a is a side view of the tool

[0022]FIG. 1b is a bottom view of the tool

[0023]FIGS. 2a, 2 b and 2 c show the attachment of the tool to the resincartridge and the insertion of the assembly into a bore hole

[0024]FIGS. 3a, 3 b, 3 c and 3 d show the operation of the tool and thepuncturing of the resin cartridge.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The term mine in the present specification is intended to includequarries, tunnels and all underground earthworks. The term roof isintended to include not only an overhead surface but also walls and allsurfaces into which anchor bolts are inserted.

[0026] According to a further aspect of the present invention there isprovided a tool for use with a cartridge to puncture the cartridge saidtool comprising a base of suitable size and cross section to be insertedin a bore hole and, extending from the base one or more sharp elementsdisposed so that when the tool is located in a bore hole with the basetowards the bottom of the hole, the elements project towards the mouthof the hole. Referring to FIGS. 1a and 1 b, the tool of total height Hcomprises a top cylindrical portion 1 of outer diameter D equal to thecartridge diameter and thickness t equal to 0.5H, with a 45° chamfer ofthe upper face 2 to a depth of 0.25 t, and a lower face 3 containingeight teeth 4 equally spaced ar 45 degrees about the perimeter of 3. Ahole 5 of diameter d1=D/2 extends entirely and concentrically throughthe cylindrical portion 1 and circular channels or flutes 6 each ofradius r1=d2/2 run longitudinally along the outer surface of portion 1at a depth d and equally spaced between the teeth 4. Four rectangularthrough slots 7 of arc width w and height h are located in portion 1 ata distance of 0.75 t from lower face 3, equally spaced 90 degrees aroundD. The teeth are each of length L equal to 0.5H and their maximumdiameter is at position 8 with a magnitude represented by d2 tapering toa reduced diameter 9 of d3=0.75d2 at face 3. Each tooth tapers to apoint at the free end 10 from which a flexible finger 11 of length 1equal to 0.52D and diameter d4 equal to t/16 extends radially towardsthe disk centre at an angle of 15 degrees from horizontal towards lowerface 3. Circular channels or flutes 12 of radius r2=d2/2 runlongitudinally through the inner surfaces of teeth 4 with their axesparallel to the central axis of cylindrical portion 1 and set in theteeth at a depth of r2 at 8.

[0027] The tool is injection moulded of a hard, durable plasticsmaterial such as rhinite or nylon using a multiple stage mould thoughother materials may be used.

[0028] Referring to FIGS. 2a, 2 b and 2 c: in use the tool is pressedonto the clip 13 of the cartridge 14 bending the fingers 11 of the tooluntil they clear and wedge against the underside 15 of the clip 13thereby retaining the tool on the clip (FIG. 2b) and allowing thecartridge to be inserted into the borehole 16 in the preferredorientation with the tool end leading (FIG. 2c).

[0029] During the normal bolting cycle the roof bolt 17 is inserted intothe bore hole 16 advancing the cartridge 14 towards the top 18 of thebore hole (FIG. 3a). As the bolt insertion continues, the tool elementcontacts the end of the hole (FIG. 3b) whereupon compression of thecartridge between the bolt tip 19 and the teeth 4 of the tool is begunsufficiently to puncture the ball end 20 of the cartridge (FIG. 3c).Continued insertion of the bolt serves to implement the flat bolt tip 19as a plunger to extrude the resin contents 21 of the cartridge from thepunctured end 20 thus affording annular flow of the resin contentsbetween the cartridge skin 22 and bore hole wall 23 as illustrated inFIG. 3d.

1. A method for installing a roof bolt in a mine which method comprises(i) drilling a hole in the roof of a mine (ii) inserting a resincartridge having a skin into the hole (iii) inserting a bolt into thehole and which comprises employing in the hole a tool s having one ormore sharp elements and wherein the insertion of the bolt causes thetool to puncture the cartridge and prevent the skin from expandingagainst the wall of the hole.
 2. A method as claimed in claim 1 whichcomprises inserting the tool into the bore hole prior to the cartridge.3. A method as claimed in claim 1 which comprises attaching the tool tothe leading end of the cartridge prior to insertion in the hole so thatthe sharp elements point towards the cartridge.
 4. A method as claimedin claim 1 which comprises attaching the tool to the tip of the bolt sothat the sharp elements point towards the cartridge.
 5. An assembly foruse in roof bolting said assembly comprising: a cartridge and attachedto one end thereof a tool having a sharp element which on theapplication of pressure in the bore hole is capable of puncturing theskin of the cartridge and depressurising the cartridge.
 6. An assemblyas claimed in claim 5 wherein the tool is attached to the clip of thecartridge.
 7. An assembly as claimed in claim 5 or 6 wherein the sharpelement comprises a plurality of teeth arranged so that when theassembly is inserted into a bore hole the teeth project towards thecartridge.
 8. A tool for use with a cartridge to puncture the cartridgesaid tool comprising: a base of suitable size and cross section to beinserted in a bore hole and, extending from the base one or more sharpelements disposed so that when the tool is located in a bore hole withthe base towards the bottom of the hole, the element projects towardsthe mouth of the hole.